A comparative study of the self-propelled jumping capabilities of coalesced droplets on RTV surfaces and superhydrophobic surfaces

Abstract

Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties. However, to date self-propelled jumping phenomenon has only been observed and studied on superhydrophobic surfaces, other than those hydrophobic surfaces with weaker but fairish water-repellency, for instance, vulcanized silicon rubber (RTV) coatings. In this work, from the perspective of thermodynamic-based energy balance aspect, the reason that self-propelled jumping phenomenon does not happen on RTV coatings is studied. The apparent contact angles of droplets on RTV coatings can be less than the theoretical critical values therefore cannot promise energy surplus for the coalesced droplets onside. Besides, on RTV and superhydrophobic surfaces, the droplet-size dependent variation characteristics of the energy leftover from the coalescence process are opposite. For the droplets coalescing on RTV coatings, the magnitudes of energy dissipations are more sensitive to the increase in droplet size, compared to that of released surface energy. While for superhydrophobic coatings, the energy generated during the coalescence process can be more sensitive than the dissipations to the change in droplet size.

Molecular simulation study of the adhesion work for water droplets on water monolayer at room temperature*

“…The present study deepens the physical mechanism behind the wetting behavior, which would have implications in the actual fabrication of novel material for water treatment, surface catalysis and self-cleaning of surfaces. [44,45]…”

The Performances of RTV Coated Surfaces and Their Services in Transmission Lines

“…Regarding superhydrophobic surface study [18], where water self-propels to coalesce droplets and jump off the surface. Since the contact angle of RTV surface is smaller than that of the superhydrophobic surface, this phenomenon does not occur on the RTV surface.…”

“…Since the contact angle of RTV surface is smaller than that of the superhydrophobic surface, this phenomenon does not occur on the RTV surface. Their mechanism is described in Figure 6 [18]. The reason of this phenomenon is that the roughness of the material surface is different and causes different contact modes, as shown in Figure 7 [16].…”

An Amphiphilic Surface with Improved Thermal Radiation for Water Harvesting

“…The surface polarity and free energy of solids are vital indicators influencing a droplet’s nucleation efficiency during water harvesting [ 6 , 7 , 8 , 9 , 10 ]. Wang et al [ 11 ] found that the wettability of different surfaces was due to droplets sliding with different rhythms. Pogorzelski et al [ 12 , 13 ] suggested that clean metal surfaces have a higher surface tension and hydrophilicity, which can improve the heat exchange efficiency between water vapor and solid surfaces.…”